Exceptions: The failwith Function (F#)
The failwith function generates an F# exception.
The error-message-string in the previous syntax is a literal string or a value of type string. It becomes the Message property of the exception.
The exception that is generated by failwith is a Microsoft.FSharp.Core.FailureException exception, which is a reference that has the name Failure in F# code. The following code illustrates the use of failwith to throw an exception.